When the human body becomes a walking memory of evidence, sound waves are the only password - he sings at the sewage outlet just to let thirty skeletons speak.
In the Doomsday Gears, each other's flesh is forged into a dagger piercing the darkness. This emotion is like a lily of the valley soaked in sewage - the more the roots rot, the more the flowers bloom with a strange blue light.
Purpose: Civilized ethics, environmental protection